14. 14
MW (Molecular Weight) = sum of the weights of
atoms in a molecule
mEq (milliequivalents) = MW (in mg)/ valence
mOsm (milliosmoles) = number of particles in a
solution
19. 19
Movement of body fluids
“ Where sodium goes, water follows.”
Diffusion – movement of particles down a
concentration gradient.
Osmosis – diffusion of water across a
selectively permeable membrane
Active transport – movement of particles up
a concentration gradient ; requires energy
20. 20
ICF to ECF – osmolality changes in ICF not
rapid
IVF → ISF → IVF happens constantly due to
changes in fluid pressures and osmotic forces
at the arterial and venous ends of capillaries
22. 22
Regulation of body water
• ADH – antidiuretic hormone + thirst
– Decreased amount of water in body
– Increased amount of Na+ in the body
– Increased blood osmolality
– Decreased circulating blood volume
• Stimulate osmoreceptors in hypothalamus
ADH released from posterior pituitary
Increased thirst
25. 25
Dysfunction or trauma can cause:
Decreased amount of water in body
Increased amount of Na+
in the body
Increased blood osmolality
Decreased circulating blood volume
26. 26
Edema is the accumulation of fluid within the
interstitial spaces.
Causes:
increased hydrostatic pressure
lowered plasma osmotic pressure
increased capillary membrane permeability
lymphatic channel obstruction
27. 27
Hydrostatic pressure increases due to:
Venous obstruction:
thrombophlebitis (inflammation of veins)
hepatic obstruction
tight clothing on extremities
prolonged standing
Salt or water retention
congestive heart failure
renal failure
28. 28
Decreased plasma osmotic pressure:
↓ plasma albumin (liver disease or
protein malnutrition)
plasma proteins lost in :
glomerular diseases of kidney
hemorrhage, burns, open wounds
and cirrhosis of liver
30. 30
Fluid accumulation:
increases distance for diffusion
may impair blood flow
= slower healing
increased risk of infection
pressure sores over bony
prominences
Psychological effects
31. 31
Edema of specific organs can be life
threatening (larynx, brain, lung)
Water is trapped, unavailable for metabolic
processes. Can result in dehydration
and shock. (severe burns)
32. 32
Electrolyte balance
• Na +
(Sodium)
– 90 % of total ECF cations
– 136 -145 mEq / L
– Pairs with Cl-
, HCO3
-
to neutralize charge
– Low in ICF
– Most important ion in regulating water balance
– Important in nerve and muscle function
37. 37
Isotonic alterations in water
balance
• Occur when TBW changes are
accompanied by = changes in electrolytes
– Loses plasma or ECF
– Isotonic fluid loss
• ↓ECF volume, weight loss, dry skin and
mucous membranes, ↓ urine output, and
hypovolemia ( rapid heart rate, flattened
neck veins, and normal or ↓ B.P. – shock)
38. 38
• Isotonic fluid excess
– Excess IV fluids
– Hypersecretion of aldosterone
– Effect of drugs – cortisone
Get hypervolemia – weight gain, decreased
hematocrit, diluted plasma proteins, distended
neck veins, ↑ B.P.
Can lead to edema (↑ capillary hydrostatic
pressure) pulmonary edema and heart failure
39. 39
Electrolyte imbalances: Sodium
• Hypernatremia (high levels of sodium)
–Plasma Na+ > 145 mEq / L
–Due to ↑ Na + or ↓ water
–Water moves from ICF → ECF
–Cells dehydrate
41. 41
• Hypernatremia Due to:
–Hypertonic IV soln.
–Oversecretion of aldosterone
–Loss of pure water
• Long term sweating with chronic fever
• Respiratory infection → water vapor
loss
• Diabetes – polyuria
–Insufficient intake of water (hypodipsia)
44. 44
Hyponatremia
• Overall decrease in Na+ in ECF
• Two types: depletional and dilutional
• Depletional Hyponatremia
Na+ loss:
– diuretics, chronic vomiting
– Chronic diarrhea
– Decreased aldosterone
– Decreased Na+ intake
45. 45
• Dilutional Hyponatremia:
– Renal dysfunction with ↑ intake of hypotonic
fluids
– Excessive sweating→ increased thirst →
intake of excessive amounts of pure water
– Syndrome of Inappropriate ADH (SIADH) or
oliguric renal failure, severe congestive heart
failure, cirrhosis all lead to:
• Impaired renal excretion of water
–Hyperglycemia – attracts water
46. 46
Clinical manifestations of
Hyponatremia
• Neurological symptoms
– Lethargy, headache, confusion, apprehension,
depressed reflexes, seizures and coma
• Muscle symptoms
– Cramps, weakness, fatigue
• Gastrointestinal symptoms
– Nausea, vomiting, abdominal cramps, and
diarrhea
• Tx – limit water intake or discontinue meds
47. 47
Hypokalemia
• Serum K+
< 3.5 mEq /L
• Beware if diabetic
–Insulin gets K+
into cell
–Ketoacidosis – H+
replaces K+
, which is
lost in urine
• β – adrenergic drugs or epinephrine
48. 48
Causes of Hypokalemia
• Decreased intake of K+
• Increased K+
loss
–Chronic diuretics
–Acid/base imbalance
–Trauma and stress
–Increased aldosterone
–Redistribution between ICF and ECF
49. 49
Clinical manifestations of
Hypokalemia
• Neuromuscular disorders
–Weakness, flaccid paralysis, respiratory
arrest, constipation
• Dysrhythmias, appearance of U wave
• Postural hypotension
• Cardiac arrest
• Others – table 6-5
• Treatment-
– Increase K+
intake, but slowly, preferably by
foods
50. 50
Hyperkalemia
• Serum K+ > 5.5 mEq / L
• Check for renal disease
• Massive cellular trauma
• Insulin deficiency
• Addison’s disease
• Potassium sparing diuretics
• Decreased blood pH
• Exercise causes K+ to move out of cells
51. 51
Clinical manifestations of
Hyperkalemia
• Early – hyperactive muscles , paresthesia
• Late - Muscle weakness, flaccid paralysis
• Change in ECG pattern
• Dysrhythmias
• Bradycardia , heart block, cardiac arrest
52. 52
Treatment of Hyperkalemia
• If time, decrease intake and increase renal
excretion
• Insulin + glucose
• Bicarbonate
• Ca++
counters effect on heart
53. 53
Calcium Imbalances
• Most in ECF
• Regulated by:
–Parathyroid hormone
• ↑Blood Ca++
by stimulating osteoclasts
• ↑GI absorption and renal retention
–Calcitonin from the thyroid gland
• Promotes bone formation
• ↑ renal excretion
54. 54
Hypercalcemia
• Results from:
– Hyperparathyroidism
– Hypothyroid states
– Renal disease
– Excessive intake of vitamin D
– Milk-alkali syndrome
– Certain drugs
– Malignant tumors – hypercalcemia of malignancy
• Tumor products promote bone breakdown
• Tumor growth in bone causing Ca++
release
55. 55
Hypercalcemia
• Usually also see hypophosphatemia
• Effects:
– Many nonspecific – fatigue, weakness, lethargy
– Increases formation of kidney stones and
pancreatic stones
– Muscle cramps
– Bradycardia, cardiac arrest
– Pain
– GI activity also common
• Nausea, abdominal cramps
• Diarrhea / constipation
– Metastatic calcification
56. 56
Hypocalcemia
• Hyperactive neuromuscular reflexes and
tetany differentiate it from hypercalcemia
• Convulsions in severe cases
• Caused by:
– Renal failure
– Lack of vitamin D
– Suppression of parathyroid function
– Hypersecretion of calcitonin
– Malabsorption states
– Abnormal intestinal acidity and acid/ base bal.
– Widespread infection or peritoneal inflammation
